Interaction of singlet oxygen [O 2 ( 1 Δ)] with aliphatic amines and hydroxylamines

Singlet oxygen quenching rates for O2(1Δ) by triethylamine, diethylamine, and N,N-diethylhydroxylamine have been measured in several solvents. The data obtained for the amines are compatible with a charge-transfer quenching mechanism; quenching is faster in solvents of high capacity to stabilize charges and low capacity to donate a proton. Quenching by N,N-diethylhydroxylamine shows a different solvent dependence: the rate constant depends upon the availability of the hydroxylic hydrogen. This fact, together with the high yields of hydrogen peroxide produced in the singlet oxygen–diethylhydroxylamine reaction, implies a different quenching mechanism.